Population and case-control studies indicate the involvement of diet in breast cancer etiology. The proposed study will examine adherence to a dietary alteration program for 300 postmenopausal stage II breast cancer patient in conjunction with chemotherapy or chemohormonal therapy. All eligible patients will be treated with CMF, those patients with ER+ nodes will also receive tamoxifen. The primary objective of the proposed study is to determine the degree to which patient will adhere to the program involving significant dietary alteration including dietary fat reductions. To monitor adherence, fat scores will be compared between patient randomly assigned to receive the low-fat dietary intervention and those whose diet is not changed. This study of adherence to a low- fat diet is a critical intermediary step in the effort to determine whether a full scale outcome study evaluating dietary addition to standard breast cancer therapy is justified. The study will be carried out in collaboration with six clinical unit and a coordinating nutrition and statistical center. During a two year period 300 patient will be accrued. Individuals recruited into the study will be randomly assigned to an Intensive Intervention group (IIG) or a Nonintensive Intervention group (NIG). Those patients assigned to the IIG will receive a step-by- step behavioral approach to dietary counseling every two weeks for the first 8 weeks, followed by 6 monthly visits. During the final 4 months of intervention, patient will receive dietary counseling every other month. Utilizing 4-day food records, 24-hour telephone recall, and biochemical variables, dietary adherence will be monitored at baseline, 3, 6 and 12 months. Patients will be followed for one year and adherence will be assessed at 18 and 24 months. In addition to the measurement of dietary compliance, the secondary objectives of this research are: 1) to identify a set of behavioral and psychosocial variables which can be used as individual predictors of dietary change, 2) to monitor fatty acids, cholesterol, triglycerides, HDL and LDL to determine the correlation of these measures with food record measures of dietary change, and 3) to investigate associations between fat scores and other dietary factors which might affect adherence.